430 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
The resemblance of head to that of Monorygma chlamedoselachi Lonnberg is very striking. The 
neck is minutely serrate in outline. The ripe segments are very easily detached. Some free segments 
which probably belonged to this species were much larger than the dimensions of the last segment 
given below. Dimensions of one in millimeters: Length, 3.77; length of head, 0.35; breadth of head, 
0. 42; diameter of neck, 0.15; distance to first segment, 1.6; last segment, length, 0.65; breadth, 0.17. 
Similar forms found in Galeocerdo and Isurus. 
4. Thysanocephalum ridiculum sp. nov. Spiral valve. [PI. xxvn, figs. 294, 295.] 
A few very small specimens with scolices which agree in minute detail with the head proper of 
T. crispum, but without the characteristic pseudoscolex of that species, were found. The head is 
quadrangular, the bothria oblong, each of the four with two short, conical hooks, which are the lateral 
prolongations of a transverse partition. The structure of these hooks is entirely different from that of 
the ordinary chitinous hooks of cestodes and acanthoeephala. It- appears to be of the same essential 
nature as the thickened borders of the bothria, but denser. This has already been shown for T. cris- 
pum (Report of U. S. Fish Commission for 1888, p. 547, pi. lxii, fig. 13). Back of the hooks the 
bothria are somewhat trough-shaped. In front of the hooks the bothria are prolonged in some, short 
in others. The contraction states are more variable in the anterior than in the posterior parts of the 
bothria. The anterior portion evidently has suctorial functions. It has the appearance of a distinct 
loculus in contraction. The strobiles are short, the proglottides rather irregular, easily detached, 
posterior ones elliptical, making the chain moniliform in outline. Dimensions in millimeters: Length, 
3.36; diameter of head at hooks, 0.72; in another, 0.26; length of bothrium, 0.75; in another, 0.44; 
breadth of bothrium, 0.50; in another, 0.17; length of hooks, 0.06; diameter of neck 0.25, swelling 
to 0.46 at 0.29 from head; in another, 0.14, swelling to 0.20 at 0.14 from head. 
5. Platybothrium parvum sp. nov. Spiral valve. 
These specimens, of which 57 were found, are identical with No. 6 under Carcharinus milberti. 
Upon superficial examination one would be disposed to place them in the genus Phoreiobothrium. The 
character of the hooks, however, is unmistakable. The longest specimens measure about 10 mm. 
They are not in good condition for measuring, being more or less coiled up. The segments drop off 
very easily. A few retained, six in one case, give to the strobile a characteristic moniliform appear- 
ance. In such cases the segments may be a little longer than broad, as long as broad or broader than 
long. For further details of this species, see under C. milberti, No. 6. 
6. Tctrarliynchus robustm Linton. Scolex, spiral valve. One scolex with beginning of strobile. [PI. 
xxi, fig. 242.] 
Squalus acanthias, Horned, Dog-Jish, Spiny Dog-Jisli. 
FOOD. 
A specimen examined by me July 26, 1900, had been confined in the pool two or three weeks. 
The alimentary tract was almost entirely empty, except a few bits of eelgrass and the test of a young 
sea-urchin 1.5 mm. in diameter. Vinal N. Edwards says he has examined the stomachs of this dog-fish 
and found them filled with ctenophores. No entozoa were found. Mr. C. F. Silvester reports that 
he finds fish of various kinds in the stomachs of spiny dog-fish from Provincetown, Mass. 
7 , p. 274. 
Raja erinacea, Summer Skate. 
FOOD. 
Usually Crustacea and annelids, but bivalve mollusks, squid, and fish also frequently found in the 
stomach. In the summer of 1899 thirty-two skates were examined and the following food material 
noted: Crabs (hermit, Cancer, Callinectes, Panopeus, and others), shrimps, amphipods, annelids, squid, 
bivalve mollusks, small fish. 
NEMATODES. 
1. Ascaris rotundata Rudolphi. Stomach and intestine. [PI. in, figs. 14-18.] 
Nematodes found on several occasions are referred to this species. Length of males, 12 to 18 mm. ; 
females, 25 to 40 mm. There are three postanal, one large and two small, and eight or nine preanal 
papillae on each side in the male. Mouth trilobed, the lips projecting into blunt papillae, and 
